PHing organics?

Allow me to clarify. My post #17 was in response to #15 in an attempt to illustrate how, from my perspective, "soil pH" is something which is dynamic, even heterogeneous to an extent. Also, I keep mentioning potting mix and containers and sphagnum peat (in case you hadn't noticed). I never said lime would lower pH. I never said you wanted to add more lime when your pH was already above 7.

I said make sure there is sufficient lime incorporated, I didn't mean to indicate you should add more if there is already enough (if there isn't in fresh mix 1-2 tbsp is generally added). And of course I am talking about potting 'soil' or soil-less mix, containing sphagnum or coir. As you just said, peat is VERY acidic. Coco coir is less so, but not typically ideal (and can use the Ca\Mg). Compost is also frequently found in potting soil. Finally, other amendments and liquid organic fertilizers\products more often than not make for fertigation water with acidic to slightly acidic pH.

The thing is that when you use dolomite in this manner it really does control pH, in the sense that it is helping soil resist sudden down swings in pH by neutralizing acids over time. And of course outdoors, in the ground, there already exists carbonates in some form such as CaCO3 or MgCO3; in some areas more than others and also applied in certain areas. Limestone deposits near aquifers or where water is drawn often have elevated levels of Ca and Mg. When carbon dioxide dissolves in water it is a weak acid, which can dissolve lime deposits, forming the soluble calcium bicarbonate (over time this leads to the formation of caverns). This is often one of the things that accounts for hard water.

I have no problem with someone saying that dolomite lime helps to control acidity over time. We just need to be careful, because so many times, a poster will be asking how to fix an overly basic soil and the advise given is to add dolomite lime. This is TERRIBLE advise and will just make things worse.
We also have to remember that lime is not the only way to add calcium and magnesium. Green leafy vegetables are FULL of magnesium.....and so is compost made from these. Oyster and egg shells, and certain types of clay are also great sources of calcium....and many of them will not cause your pH to raise as drastically as they would if you simply added lime....dolomite or otherwise.

I agree that pH can and often should be homogenous, but if you see a trend of your soil pH going to far upward, a topdressing of sulfur or earthworm compost, or adding a bit of apple cider vinegar to the water is a great way to fix this. I always prefer to use products that benefit my grow in multiple ways. Raw/unfiltered ACV adds beneficial yeasts to the soil (we want a diverse micro life including micro floura/fauna/fungi/etc), sulfur is an essential element for the development of chlorophyll and many plant proteins, as well as an effective pest deterrent. And I don't know of any better source of the organic portion of your soil than a homemade earthworm compost. A homemade product will not only be fresher and have a stronger microlife, but the worms will have had more diverse food sources and thus you will be adding a more complete plant nutrient to your grow.

If you are using a bottled "organic" line of nutrients, you are correct that acidity is often more of a problem than not, but many of us are more purists and do not use those products. Then sometimes this is not the issue. I re-iterate this simply to urge you guys who are constantly pushing dolomite lime to be careful. While I know you are trying to be helpful, dolomite lime does not "fix" or "control" pH, and depending on the OPs issue, you may end up giving them advise that will slowly kill their plants.

AliCakes said:

I have no problem with someone saying that dolomite lime helps to control acidity over time. We just need to be careful, because so many times, a poster will be asking how to fix an overly basic soil and the advise given is to add dolomite lime. This is TERRIBLE advise and will just make things worse.
We also have to remember that lime is not the only way to add calcium and magnesium. Green leafy vegetables are FULL of magnesium.....and so is compost made from these. Oyster and egg shells, and certain types of clay are also great sources of calcium....and many of them will not cause your pH to raise as drastically as they would if you simply added lime....dolomite or otherwise..

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Oyster and egg shells are primarily calcium carbonate (CaCO3)... I use egg shells myself. Throw them in a coffee grinder for about ten seconds and guess what you've got? Calcitic lime, essentially. The larger the particle size, the slower\longer acting it'll be.

Nullis said:

It depends somewhat on the brand and ingredients are in the product. Liquid pH Up and Down products are intended more for use with hydroponics setups not using any organic medium. It is the synthetic liquid pH Up that is something of a concern. Microbes don't generally like any sudden changes in pH, but some brands of pH Up contain potassium hydroxide which is antimicrobial. Earth Juice does make a natural Up and Down, but again these are really more for hydroponics. Liquid solutions are really only temporary and IMO can cause more issues in soil.

Most of us doing organics in soil or soil-less make sure we have dolomite lime incorporated into the mix before planting. Garden lime comes as calcite or dolomite lime, the former is just calcium carbonate whereas dolomite also contains magnesium. Ca and Mg are both needed plant nutrients, and cannabis tends to want a good amount of both.
Lime is perfectly safe, difficult to over-do and it neutralizes acidity over time while supplying Ca and Mg. Generally 1-2 (heaping) tablespoons per gallon of mix are added. You can also apply to containers by scratching it into the surface and then watering in thoroughly. With a deficiency or really low pH it might take a week before the plant really starts to recover.

I don't worry much about the pH of anything I apply to the soil. Microbes themselves are managing the pH in specific zones of the rhizosphere, which is where it counts.

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One thing was, and as I attempted to clarify in my second post, I assumed the OP was likely growing in containers with store-bought or mixed potting "soil"... even if he is growing outdoors. Usually when somebody is talking about pH'ing every water and worried about using it they are talking about pH Up and most probably growing in containers. Maybe it is just my own memories of how much UP I would use in attempt to get my fertigation solutions to the 'correct' pH when I first started growing. Maybe I assumed a little too much or could have been more specific...I am always forgetting to put stuff in my posts... but I never said to lime alkaline soil or that it would fix issues with high pH... that was addressed in post #8.

I don't "constantly push" dolomite lime. I didn't even say anything about it being able to "control" pH... until you said that it didn't, because someone obviously doesn't know the literal meaning of the word "control" (no offense). And yes, dolomite will also "fix" pH... when it is too low!

Nullis said:

Most potting soil\mix contains sphagnum-peat moss, which is acidic. It may also contain coco coir, as many new mixes do, and coir has a slightly more neutral pH than sphagnum. When you buy a mix like this, e.g. Ocean Forest or Sunshine Advanced #4 it comes limed, however there is often not enough initially to keep media pH in the 6.5-7 range for very long. Cannabis plants also enjoy calcium and magnesium. So if this is the case... yeah, dolomite. This is how I have been growing for quite some time indoors with rain water (or sometimes bottled water). If you use rain, distilled, bottled, RO water like I do you'll benefit from more dolomite. If you use tap or well water that has a high TDS and consequently, more dissolved minerals with a higher pH then no you wont require as much lime but a tablespoon per gallon isn't going to hurt.

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I am talking about container gardening and my experience with container gardening... with potting mix based upon materials such as sphagnum-peat, coco coir, composts, etc. And how in my experience so long as you have enough liming agent (dolomite, oyster/eggshell) to counter the acidity of the potting mix materials and amendments... you are generally all set as far as pH is concerned. This seems to work, in practice, for some reason.

But, for the last time, I never said to add dolomite outside where there was already enough liming agent naturally present.
Irksome when people try to assess the "purity" of other growers... on the internet no less.

BTW I hate to see someone worried that their pH is 6.8 or 7. If someone does add too much lime to their potting mix you can simply mix in more sphagnum peat, coco coir or compost. Unless you're using tap water which is hard and alkaline, the pH is likely to drop a little bit and this is especially true if you have a significant amount of ammoniacal-N in the fertilizer you use.